Which colony was established in 1665 when New Haven and Hartford came together?

The establishment of the colony in 1665 from the merger of New Haven and Hartford is Connecticut. This came about due to the desire for more centralized governance and to unify the Puritan settlements in the region. The Fundamental Orders of 1638-1639, which established a representative government in Hartford, laid the groundwork for this unification. The integration of New Haven, which had its own set of religiously-influenced laws and governance, into Connecticut reflected a broader trend of consolidation among colonies in search of stability and more effective governance, particularly in the wake of conflicts such as King Philip's War.

By 1665, the colony was recognized for its unified political structure that allowed for greater cooperation among diverse settlements, emphasizing the importance of community and governance in colonial America. This historical context further solidifies that Connecticut was indeed the result of this merger, making it the correct answer to the question.